Add examples (#66)

Added examples and proc macros

Cargo.toml

@@ -19,4 +19,11 @@ categories = [
     "aerospace::protocols",  
     "no-std::no-alloc", 
     "parser-implementations"
-]
+]
+
+[features]
+default = [ "derive" ]
+derive = [ "dep:mil_std_1553b_derive" ]
+
+[dependencies]
+mil_std_1553b_derive = { path = "crates/mil_std_1553b_derive", optional = true }

crates/mil_std_1553b_derive/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "mil_std_1553b_derive"
+version = "0.4.0"
+edition = "2021"
+license = "MIT"
+readme = "README.md"
+description = "MIL STD 1553B proc macros"
+authors = ["Michael House <[email protected]>"]
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "1.0", features = ["full"]}
+quote = "1.0"
+proc-macro-error = "1.0.4"
+proc-macro2 = "1.0.79"

crates/mil_std_1553b_derive/README.md

@@ -0,0 +1,3 @@
+# MIL STD 1553B Derives
+
+Provides proc-macros for deriving mil_std_1553b types.

crates/mil_std_1553b_derive/src/field.rs

@@ -0,0 +1,43 @@
+use proc_macro::TokenStream;
+use proc_macro_error::OptionExt;
+
+pub struct FieldArgs {
+    name: Option<String>,
+    value: Option<String>
+}
+
+impl FieldArgs {
+    pub fn new(input: TokenStream) -> Self {
+        let mut items = input.into_iter();
+
+        let name = items
+            .next()
+            .map(|t| t.to_string());
+
+        // skip the comma
+        items.next();
+
+        let value = items
+            .next()
+            .map(|t| t
+                .to_string()
+                .trim_start_matches("0b")
+                .to_string());
+
+        Self { name, value }
+    }
+
+    pub fn name(&self) -> String {
+        self.name
+            .clone()
+            .expect_or_abort("Need an identifier for the field")
+    }
+
+    pub fn mask(&self) -> u16 {
+        self.value
+            .clone()
+            .and_then(|v| u16::from_str_radix(&v,2).ok())
+            .expect_or_abort("Need a mask for the field")
+    }
+
+}

crates/mil_std_1553b_derive/src/lib.rs

@@ -0,0 +1,180 @@
+use proc_macro::{Span, TokenStream};
+use proc_macro_error::{abort, abort_call_site};
+use quote::{quote, ToTokens};
+use syn::{parse_macro_input, DeriveInput, Ident, ItemFn};
+
+mod word;
+mod field;
+
+use field::FieldArgs;
+use word::FieldKind;
+
+/// Derive the `Word` trait and associated From implementations
+/// 
+/// This trait requires that the `Default` trait is implemented
+/// as well. To avoid this, implement the Word trait manually.
+/// 
+/// ### Example
+/// 
+/// ```rust
+/// #[derive(Default, Word)]
+/// struct MyWord {
+///  
+///     #[data]
+///     buffer: [u8; 2],
+///
+///     #[parity]
+///     parity_bit: u8,
+///
+///     // you can have any other
+///     // fields you need
+///     count: u8,
+/// }
+/// ```
+#[proc_macro_derive(Word, attributes(data,parity))]
+#[proc_macro_error::proc_macro_error]
+pub fn word_derive(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    let item = match input.data {
+        syn::Data::Struct(s) => s,
+        _ => abort_call_site!("Word derive is only valid on a struct")
+    };
+
+    let fields = match item.fields {
+        syn::Fields::Named(n) => n,
+        _ => abort_call_site!("Word derive requires named fields")
+    };
+
+    let mut data_field: FieldKind = FieldKind::None;
+    let mut parity_field: FieldKind = FieldKind::None;
+
+    for named in fields.named {
+        match word::parse_field(&named) {
+
+            word::FieldKind::Data(v) if data_field.is_some() => 
+                abort!(v, "Duplicate #[data] fields"),
+
+            word::FieldKind::Parity(v) if parity_field.is_some() => 
+                abort!(v, "Duplicate #[parity] fields"),
+
+            k if k.is_data() => data_field = k,
+            k if k.is_parity() => parity_field = k,
+            _ => continue
+        }
+    }
+
+    if data_field.is_none() {
+        abort!(data_field.ident(),"Need a '#[data]' field with type '[u8;2]'");
+    }
+
+    if parity_field.is_none() {
+        abort!(parity_field.ident(),"Need a '#[parity]' field with type 'u8'");
+    }
+
+    let self_type = input.ident;
+
+    let data_ident = data_field.ident();
+
+
+    let word_impl = word::impl_word(&data_field, &parity_field, &self_type);
+
+    quote!(
+        #word_impl
+
+        impl From<&mil_std_1553b::DataWord> for #self_type {
+            fn from(word: &mil_std_1553b::DataWord) -> Self {
+                use mil_std_1553b::Word;
+                #self_type::new()
+                    .with_bytes(word.as_bytes())
+                    .with_parity(word.parity())
+            }
+        }
+
+        impl From<&#self_type> for  mil_std_1553b::DataWord {
+            fn from(word: &#self_type) -> Self {
+                use mil_std_1553b::Word;
+                mil_std_1553b::DataWord::new()
+                    .with_bytes(word.as_bytes())
+                    .with_parity(word.parity())
+            }
+        }
+
+        impl From<mil_std_1553b::DataWord> for #self_type {
+            fn from(word: mil_std_1553b::DataWord) -> Self {
+                Self::from(&word)
+            }
+        }
+
+        impl From<#self_type> for  mil_std_1553b::DataWord {
+            fn from(word: #self_type) -> Self {
+                Self::from(&word)
+            }
+        }
+
+        impl From<&#self_type> for  u16 {
+            fn from(word: &#self_type) -> Self {
+                u16::from_be_bytes(word.#data_ident)
+            }
+        }
+
+        impl From<#self_type> for  u16 {
+            fn from(word: #self_type) -> Self {
+                u16::from_be_bytes(word.#data_ident)
+            }
+        }
+    ).to_token_stream().into()
+}
+
+/// Implement a parser for a word field
+/// 
+/// ### Arguments
+/// 
+/// * name - A const name for the field (e.g. 'MY_FIELD')
+/// * mask - A u16 bit mask for the field (e.g. '0b10000000000000000')
+/// 
+/// ### Example
+/// 
+/// ```rust
+/// 
+/// #[field(MY_FIELD, 0b1000000000000000)]
+/// pub fn get_my_field_value(&self) -> u8 { 
+///     Self::MY_FIELD.get(self)
+/// }
+/// 
+/// ```
+/// 
+/// Will generate the following code:
+/// 
+/// ```rust
+/// 
+/// pub const MY_FIELD_MASK: u16 = 32768u16;
+/// pub const MY_FIELD: Field = Field::from(Self::MY_FIELD_MASK);
+/// pub fn get_my_field_value(&self) -> u8 {
+///     Self::MY_FIELD.get(self)
+/// }
+/// 
+/// ```
+#[proc_macro_attribute]
+#[proc_macro_error::proc_macro_error]
+pub fn field(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let args = FieldArgs::new(attr);
+    let item = parse_macro_input!(item as ItemFn);
+
+    let name = args.name();
+    let mask = args.mask();
+
+    let mask_label = format!("{}_MASK",name);
+    let mask_ident = Ident::new(&mask_label, Span::call_site().into());
+
+    let field_label = format!("{}",name);
+    let field_ident = Ident::new(&field_label, Span::call_site().into());
+
+    quote!(
+        pub const #mask_ident: u16 = #mask;
+
+        pub const #field_ident: Field = Field::from(Self::#mask_ident);
+
+        #item
+    ).to_token_stream().into()
+}